In the case of this tried-and-tested construction of semiconductor modules that is known per se (DE 197 21 061 A1), usually one or more power semiconductor chips are arranged on a substrate and contacted on the rear side. The underside of the substrate is copper-clad and acts as a heat-dissipating contact area, to allow power losses occurring in the form of heat to be dissipated during the operation of the semiconductor components. For this purpose, it is surface-connected to a base plate, for example by soldering.
This arrangement is surrounded by a frame or (plastic) module housing and may be pressed onto a heat sink, for example by means of screwed connections. The generalizing term housing is to be understood hereafter as meaning both a frame, which may also be part of a multipart housing, and a module housing. For optimum heat dissipation, planar, complete surface contact is desired between the underside of the base plate and a cooling element or heat sink that dissipates heat, for example by convective air flow.
To maintain adequate surface contact, however, significant pressing forces are required, usually achieved by the module user or final customer by means of screwed connections. The pressing forces thereby act via the housing, and consequently also on the housing. Depending on the housing material that is used, it has the tendency in the long term to undergo material deformations caused by so-called flowing. In other words, the form of the housing in the region of the connections or where the force is introduced is not stable in the long term, so that the connections become loose and consequently the pressing forces are undesirably reduced. This is problematical in particular in the case of the widespread use of plastic housings.